1. Field of the Invention
The present invention is directed to the design of a power substrate utilizing silver conductors on ceramic, and the process for making the device.
2. Description of the Known Art
The role of a power substrate in power electronics applications is to provide both electrical interconnections between components and systems, as well as to dissipate large amounts of heat to cool the active electrical components. These substrates must be able to withstand both high temperatures, as well as thermal cycling. Common substrates used for power applications include direct bond copper (DBC), direct bond aluminum (DBA), and active metal braze (AMB), and the ceramic used commonly in these substrates are alumina, silicon nitride, aluminum nitride, and beryllium oxide.
Patents disclosing information relevant to electrical circuit and trace formation include: U.S. Pat. No. 8,043,536, issued to Inaba, et al., on Oct. 25, 2011 entitled Silverpalladium alloy containing conductor paste for ceramic substrate and electric circuit; U.S. Pat. No. 6,541,859, issued to Forbes, et al. on Apr. 1, 2003, entitled Methods and structures for silver interconnections in integrated circuits; U.S. Pat. No. 7,732,002 issued to Kodas, et al. on Jun. 8, 2010 entitled Method for the fabrication of conductive electronic features; U.S. Pat. No. 7,691,664 issued to Kodas, et al. on Apr. 6, 2010 entitled Low viscosity precursor compositions and methods for the deposition of conductive electronic features; and U.S. Pat. No. 7,629,017 issued to Kodas, et al. on Dec. 8, 2009 entitled Methods for the deposition of conductive electronic features. United States Patent Application No. 20100104829 A1, filed by KEUSSEYAN; ROUPEN LEON on Apr. 29, 2010 entitled PROCESS FOR THICK FILM CIRCUIT PATTERNING. Each of these references are hereby incorporated in their entirety.
The prior art teaches that silver will not adhere to the surface of a substrate such that one must use compositions that reduce the conductivity of the surface traces. The present invention teaches a direct contrast to the prior art by teaching a three dimensional trench traces of pure silver for high conductivity. The trench provides sufficient contact area for the necessary level of adhesion.